1. Field of the Invention
The present invention relates generally to a microstrip antenna for use on a missile or the like. More specifically, the present invention relates to a microstrip antenna which receives GPS (global positioning system) data and which is adapted for use on small diameter projectiles such as a missile.
2. Description of the Prior Art
A microstrip antenna operates by resonating at a frequency. The conventional design for a MICROSTRIP antenna utilizes printed circuit board techniques mounting a copper patch on the top layer of a dielectric with a ground plane on the bottom of the dielectric. The frequency at which the antenna operates is approximately a half wavelength in the microstrip medium of dielectric below the copper patch and air above the copper patch.
However, there is a need to isolate the microstrip antenna from radio frequency signals at different frequencies than the operating frequency for the antenna. There is also a need to protect the antenna and to provide for signal amplification.
To achieve isolation, protection and amplification, prior art microstrip antenna designs have used an external filter, an external amplifier with a built-in limiter or an external limiter. All of these external components require extra space, which is generally not available on weapons systems, such as small diameter projectiles, and also require interconnecting coaxial cables, which are expensive and not practical when there are severe limitations on available apace in weapons systems.
Accordingly, there is a need for a microstrip antenna which operates in the GPS frequency band, requires minimal space, and provides for isolation, protection and amplification. More specifically, there is a need for a GPS frequency band microstrip antenna which generates an omni-directional antenna pattern, provides for a 25 dB minimum amplification with amplifier protection and has 30 dB isolation from a frequency of 2 GHz to a frequency of 7 GHz.